/Engine/Source/Runtime/Core/Public/Tasks/TaskPrivate.h
ExecutionFlag_ is set at the beginning of execution as the most significant bit ofNumLocks_ and indicates a switch of `NumLocks_ from "execution prerequisites" (a number of uncompleted prerequisites that block task execution) to "completion prerequisites" (a number of nested uncompleted tasks that block task completion)
static constexpr uint32 ExecutionFlag = 0x80000000;